1. Field of the Invention
The invention relates generally to axial flow combines and more particularly to sensing crop losses from the threshing region and also from the grain cleaning region of the combine.
2. Prior Art
Several patents are known to Applicant which show grain loss or flow rate monitors disposed within combines: U.S. Pat. Nos. 3,935,866, 3,638,695, 3,610,252, 3,606,745, 3,515,144, 3,563,013 and East German Pat. No. 53,446. Some of these patents relate to controlling ground speed in response to grain losses while others simply indicate losses or flow rates at selected points.
None of these patents shows or relates to axial flow type combines. An axial flow combine includes a cylindrical rotor driven at high speeds to effect the threshing and separating functions in conjunction with associated concaves and grates. The high speed of the axial flow rotor causes the crop material to be discharged through the grates at high velocity and with high kinetic energy. And therein lies the basis of a problem when it is desired to monitor material flow rates or grain losses.
State-of-the-art sensors for monitoring flow rates or material losses include transducers (U.S. Pat. No. 3,935,866 for example) disposed in the path of material flow and upon which the material impacts and from which readings are translated to the machine operator through known electronic circuitry. When used in an axial flow combine to monitor flow rates from the rotor, such a transducer is subject to the high kinetic energy of the material resulting in high rates of wear and rapid deterioration of the transducer.
The kinetic energy (E=1/2mv.sup.2) of the material is proportional to the second power of the velocity and only to the first power of the mass such that particles differing only slightly in mass but traveling at the same velocity assume nearly indentical impact characteristics on a transducer. This is particularly the case under low mass, high velocity conditions. Thus, a grain loss system that discriminates grain particles from stems, joints, and other crop material will be ineffective under the high kinetic energy conditions associated with axial flow rotors.
Another problem area is in the proper placement of the sensors to consistently sample the discharged material as to content of the flow and the ratio of sampled flow to total flow. Further, the sensors should not impede the material flow so as to cause bridging or blocking of the material. And since the combine includes several different but interrelated systems (such as a grain separating system and a grain cleaning system), the problem exists of how to position the sensors to provide an indication of the efficiency of the various systems per se and relative to each other.